Existing gripper type material feeding devices utilize a movable linearly guided gripper mechanism for feeding a strip-like workpiece. Such gripper style feeding apparatus typically utilize cams for the actuation of the opening or closing function of the gripper mechanisms to clamp and unclamp the material. Such devices are exemplified in U.S. Pat. Nos. 6,283,352 and 6,213,369. Such devices utilize a linkage arrangement or other transmission elements between the cam actuator and the gripper mechanism having a pivot axis which is parallel to the direction of workpiece motion. The disadvantage of such arrangements is that a linear sliding or linear rolling motion must be provided somewhere between the actuator and the linearly guided gripper mechanism to allow unconstrained feeding motion. This linear sliding or linear rolling motion suffers from high wear characteristics and high maintenance costs. Furthermore, mechanical adjustments are necessary to modify the timing of the opening or closing function of the gripper mechanism, or to modify the gap between the gripping members of the gripper mechanism for adaptation to different workpiece thicknesses.
Other existing gripper type material feeding devices utilize pneumatic or hydraulic cylinders for the actuation of the opening or closing functions of the gripper mechanisms. Examples of such devices are seen in U.S. Pat. Nos. 5,505,360 and 5,909,835. In such devices the cylinder actuator is transported on the linearly guided gripper mechanism. The disadvantage of such devices is that additional mass of the moving actuator limits the operational speed of the feeding device.
There exists then the need for a gripper type material feeding apparatus which does not require a sliding or rolling connection between a linearly guided gripping mechanism and the actuator for the opening or closing function of the gripping mechanism. Furthermore there exists the need for a gripper type material feeding apparatus which may utilize an actuator of high power capacity to facilitate high gripping forces and where the actuator need not be located on and moving with the gripper mechanism thereby allowing a lightweight construction of the gripper mechanism for operation at high speeds.
Furthermore there exists a need for a gripper type material feeding apparatus which does not require mechanical adjustments to modify the timing relationship between the opening or closing function of the gripper mechanisms to facilitate the piloting function of the press tooling, or to modify the gap between the gripping members of the gripper mechanisms for adaptation to different workpiece thicknesses.